Eating a diet with lots of added sugars might make a person more susceptible to kidney stones, according to new research.
The study, published Friday in Frontiers in Nutrition, suggests that reducing added sugar consumption could lower a person’s risk of developing kidney stones. Added sugars are found in many processed foods, and especially so in sugar-sweetened sodas, fruit drinks, candy, ice cream, cakes, and cookies.
The reach of the research could be vast, as it’s estimated that about 10% of Americans will develop kidney stones at some point in their lifetimes.
More research is needed to say definitively if added sugar is causing kidney stones, Shan Yin, MD, study author and doctor of urology in the Affiliated Hospital of North Sichuan Medical College in Nanchong, China, told Health in an email.
However, the study does support the idea that there is some association between the two.
“We’ve known for some time that processed foods and sugars increase risk of kidney stones,” Anna Zisman, MD, director of the kidney stone prevention program at the University of Chicago Medicine, told Health. “I think the study is quite confirmatory and should impact on how we eat, and [how we] counsel our kidney stone patients.”
Here’s what experts had to say about why people’s diets can impact their kidney stone risk, and how to best avoid kidney stones.
Kidney Stones Associated With Added Sugar Consumption
The true cause of kidney stones is a bit of a mystery, and there aren’t any foolproof treatments to completely prevent them, Dave Friedlander, MD, MPH, assistant professor of urology at the University of North Carolina School of Medicine, told Health.
In general though, kidney stones form when people get “an overabundance of certain minerals in the urine that accumulate and eventually form a crystallized stone,” Friedlander explained. Not only can they can become extremely painful, but they may also lead to infections, swollen kidneys, renal insufficiency, and even end-stage renal disease.
There are already a few known risk factors for kidney stones—including being an adult male or having obesity, chronic diarrhea, dehydration, inflammatory bowel disease, diabetes, and gout.
This newest research suggests that consumption of added sugars might also be worth adding to the list.
“The researchers were particularly interested in understanding whether or not there was association between self-reported levels of sugar consumption and self-reported renal colic episodes, or kidney stones,” Friedlander said.
For the study, Yin and his colleagues analyzed data from more than 28,300 participants in the National Health and Nutrition Examination Survey (NHANES), collected between 2007 and 2018.
Study participants, made up of both women and men, were at least 20 years old, and self-reported if they had a history of kidney stones. Researchers estimated each participant's daily intake of added sugars, based on two interviews regarding what they had recently eaten. (Participants were specifically asked if they'd had any syrups, honey, dextrose, fructose, or pure sugar in the past 24 hours).
From there, each participant also received a healthy eating index score, summarizing their diets, looking at both beneficial components (fruits, vegetables, and whole grains) and potentially harmful foods (refined grains, sodium, saturated fats).
After adjusting for adjusting for certain factors like age, race, gender, and clinical comorbidities like diabetes, the researchers found that the percentage of energy intake (calories) from added sugars in a person's diet was associated with a higher prevalence of kidney stones, Yin said.
People who derived more than 25% of their total calories from added sugars had an 88% higher risk of developing kidney stones than people who derived less than 5% of their total calories from added sugars.
The study also showed that participants from 'Other' ethnicities—like Native American or Asian people—were more likely to develop kidney stones when exposed to large amounts of added sugars, compared to Mexican American, other Hispanic, non-Hispanic White, and non-Hispanic Black people.
Diet's Impact on Kidney Stone Risk
The new research doesn't prove that added sugars cause kidney stones; instead, it only shows an association between the two. The makeup of the study, which was observational in nature and relied on self-reported data, is also a limitation.
"Further studies are needed to explore the association between added sugar and various diseases or pathological conditions in detail," Yin said in a news release.
"For example, what types of kidney stones are most associated with added sugar intake? How much should we reduce our consumption of added sugars to lower the risk of kidney stone formation? Nevertheless, our findings already offer valuable insights for decision-makers," Yin added.
Consumption of added sugars aside, previous research has shown that other aspects of diet play a large role in kidney stone risk, Zisman said.
Three types of kidney stones—calcium stones, uric acid stones, and cystine stones—have largely been associated with diet.
Calcium stones (calcium oxalate stones and calcium phosphate stones) are linked to increased consumption of oxalate-rich foods (nuts, legumes, rhubarb, spinach, and wheat bran), sodium, and animal proteins. Calcium stones, however, are not associated with increased calcium intake—instead, it's recommended that people with calcium stones get enough calcium from food sources.
Uric acid stones are also associated with eating more animal protein and people with a history of uric acid stones may want to get their protein from other plant-based sources. Drinking enough water is the most important lifestyle factor for cystine stones.
Assessing Risks to Avoid Kidney Stones
Kidney stones may affect one in 10 in the U.S., but their presentation can vary quite widely.
“It can range from being completely asymptomatic,” Zisman said, “[to being] a chronic burden where people are passing stones on a weekly or monthly [basis].”
In these cases, symptoms are "not subtle," so kidney stones result in high rates of emergency room visits and billions in healthcare costs, she explained. People can experience nausea, vomiting, blood in their urine, fevers, and severe flank pain, or pain in the abdomen below the ribs, she said.
It’s especially important that people be aware of kidney stones, as their prevalence has been increasing globally over the past three decades. Highly-processed and generally unhealthy diets may be in part to blame, Zisman said. Luckily, this is typically something that a person can improve upon.
Even though the study didn’t confirm that added sugar is causing kidney stones per se, reducing added sugar consumption may not be a bad idea—that might also help lower risks of cardiovascular disease, cognitive issues, diabetes, obesity, and some cancers.
But beyond diet, more individual lifestyle factors should be considered, too.
Having a family history of kidney stones raises risk, as does living in the Southeast, Friedlander explained. Kidney stones may also be more common or severe among people with certain jobs or socioeconomic statuses, or among people with certain conditions, such as diabetes or Crohn’s disease.
For the average person though, Zisman said the best thing to do is to maintain a healthy lifestyle and generally take things in moderation. Even just exercising frequently and maintaining a healthy weight may lower a person's risk of kidney stones, Yin added.
“If somebody does have a history of kidney stones, then we would want to evaluate their individual risk factors,” she said. “[But generally] just avoiding processed foods and extra added sugars is a good idea for a variety of health reasons, including kidney stone production.”